Engine device for reducing unburned hydrocarbons



June 13, 1961i w. A. LOBDELL ETAL 2,988,074

ENGINE DEVICE FOR REDUCING UNBURNED HYDROCARBONS Filed April 22, 1960 2 Sheets-Sheet 1 Pim/90 .ADVANCE sm m/d/ d T n N moz, WJ m 1l c r 4m w? Y B fwd M w 0 w m m w 11N@ June 13, 1961 w. A. LOBDELL ETAL Y 2,988,074

ENGINE DEVICE FOR REDUCING UNBURNED HYDRocARBoNs Filed April 22, 1960 2 Sheets-Sheet 2 Q n u I I 1- 1i l TA1 INVENToR nired States Patent@ ENGINE DEVICE FOR REDUCING UNBURNED HYDROCARBONS Wallace A. Lobdell, Taylor, and Robert J. Templin, Birmingham, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Apr. 22, 1960, Ser. No. 23,958 7 Claims. (Cl. 123-97) The present invention relates to a charge forming device for an internal combustion engine constructed so as to considerably reduce the emission of unburned hydrocarbons from the engine. More specifically, the present invention relates to a mechanism which is designed to eliminate unburned hydrocarbons during vehicle coasting operation.

It is well known in the automotive fuel systems art that during vehicle coasting conditions fuel continues to be drawn through the carburetor even though the throttle is closed and as a consequence unburned hydrocarbons are discharged through the vehicle exhaust system resulting in a contamination of the atmosphere. In the past, various types of mechanisms have been developed to overcome this emission of unburned fuels. The most common approach has been to provide for positively cutting off the Iflow of yfuel during coasting operation.

In general, coasting fuel shut-off devices have not proved to be commercially acceptable for several reasons, one of which has been the cost and complication of such devices. In addition, however, cutting off the ilow of fuel during coasting operation has had a very denite operating disadvantages in that the carburetor fuel sup ply lines as well as the intake manifold are dried out during coasting operation. As a consequence, when the operator again desires to resume normal driving operation the engine has frequently stalled for want of fuel and a denite jerk or bump is felt in restarting of the engine.

In the present invention, when the vehicle is coasting, means is provided for slightly opening the throttle whereby sufficient air is admitted to the engine to maintain a combustible mixture in the combustion chamber, even in the presence of the high exhaust gas dilution which occurs under coasting conditions. In this way the fuel is completely combusted leaving the exhaust relatively free of unburned hydrocarbons. At the same time, means is provided for retarding the engines spark so that the fuel-air mixture being burned during coasting does not contribute to a significant power output from the engine.

More specifically, the present invention includes a manifold vacuum responsive diaphragm device which is connected to both the throttle and the engine spark distributor in such a way that under normal engine operating conditions the throttle is controlled by the operator and the distributor is controlled in its normal manner. However, under conditions of abnormally high manifold vacuum, as would occur during engine vehicle coasting conditions, the diaphragm device will be actuated to move the throttle to a slightly opened position and also to rotate the distributor to retard the spark.

The details as well as other objects and advantages of the present invention will be apparent from a perusal of the detailed description which follows.

In the drawings:

FIGURE l is a diagrammatic representation of the fuel system embodying the present invention;

FIGURE 2 is an elevational view of an actual embodiment of the subject invention; and

FIGURE 3 is a plan view of FIGURE 2.

Referring to the drawings, a carburetor is indicated generally at including an induction passage 12 and a lCe throttle valve 14 rotatably disposed therein. The carburetor on which the subject invention has been illustrated in FIGURES 2 and 3 is of the four-barrel type in which second induction passages 16 are provided in addition to primary induction passages 12. Insofar as the present invention is concerned, only the primary induction passage 12 and the primary throttle 14 are involved.

Throttle 14 is fixed to a shaft 18 extending outwardly from the carburetor and having a throttle control lever 20 fixed to one end thereof. Throttle 14 is adapted to be controlled by the operator in any well known manner by actuating an accelerator pedal suitably articulated to throttle lever 20.

A servo or diaphragm mechanism 22 is suitably secured to the carburetor casing through a bracket 24. Diaphragm device 22 includes a pair of dish-shaped casing members 26 and 28 which peripherally clamp a flexible diaphragm member 30 therebetween. Diaphragm 30 has a control rod 32 centrally secured thereto. The other end of rod 32 is adapted to coact with a slot 34 in throttle lever 20. Slot 34 provides a lost motion connection with rod 32 so that throttle 14 may be moved in an opening direction without being in any way inhibited by diaphragm device 22 to provide for normal engine operation.

Casing 26 and diaphragm 30 define a chamber 36 which is communicated with a source of manifold vacuum through a conduit 38. A spring 40 is disposed between casing 28 and a bracket 42 fixed to rod 32. Spring 40 is adjustable through a nut -44 on rod 32 so that under normal engine operating conditions the spring will overt come the iniluence of manifold vacuum acting on diaphragm 30 and maintain the diaphragm in its rightward or inoperative position in which diaphragm device 22 has no etfect on either throttle 14 or distributor 46. As noted, bracket 42 is adjustably fixed to rod 32. The other end of bracket 42 is connected to distributor 46 through a flexible cable 48 in such a way that movement of diaphragm 30 will advance or retard the spark.

As already noted, under normal operating conditions diaphragm device 22 has no operative effect on engine operation. However, under engine coasting conditions, when the engine normally has a tendency to discharge a relatively large quantity of unburned hydrocarbons in through the exhaust system, the device becomes operative. Under coasting conditions, manifold vacuum exceeds the normal operating level and moves diaphragm 30 to the left against spring 40 whereby throttle 14 is slightly opened. This opening of the throttle limits the manifold vacuum to a level where the air and fuel coming into the engine can be burned without being quenched by excessive exhaust gas dilution. In this way unburned hydrocarbons are substantially eliminated from the exhaust discharge.

At the same time, throttle opening movement of diaphragm 30 under the influence of manifold vacuum causes bracket 42 to move flexible cable 48 imparting a slight rotation to the distributor housing so as to retard the spark. This retardation of the spark advance permits the engine to continue to act as a power absorber during coasting but at the same time insure that little or no mechanical effort or power is transmitted to the crankshaft since very little combustion pressure is able to develop at the retarded spark setting.

Thus, diaphragm device 22 uniquely coacts with throttle 14 and distributor 46 to permit the combustion of fuel which would otherwise pass through the exhaust system in an unburned state and at the same time permits the combustion to take place without contributing to the power output of the engine under conditions when such added power would be undesirable.

Referring more specifically to FIGURES 2 and 3 of the drawings, the subject invention is shown on a carburetor in a commercially feasible form. In general, the description'as applied to FIGURE 1 applies to the device of FIGURES 2 and 3, however, certain structural details are provided in the commercial embodiment of the subject invention which are not shown on the diagrammatic representation of FIGURE 1. Accordingly, a brief description of the device as shown in FIGURES Z and 3 will be undertaken. Where the components of FIGURES 2 and 3 vary from those shown in FIGURE 1, a prime number will be used to differentiate.

Bracket 42 has a first arm 50 to which rod 32 is articulated. An intermediate rod 52 connects a second arm 54 of bracket 42' with throttle lever 20. Bracket 42 includes a third arm 56 having a depending portion with an aperture through which a rod 58 extends. Spring members 60 and 62 are disposed on opposite Sides of depending portion of arm 56 and seat thereagainst. The other ends of springs 60 and 62 respectively seat against a washer 64 adjustably positioned by a nut 66 threaded on rod 58 and a fixed ange 68. The other end of lrod 5S isarticulated to a U-shape lever 70 pivotally mounted upon a bracket member 72 lixed to carburetor casing 74. A flexible control cable 48 is also articulated to lever 70 outwardly of the point of articulation of rod 58 thereto. The other end of control cable 48 is connected to the breaker plate of distributor 46. The arcuate movement of lever 70 is limited by adjustable stops 76 and 78 formed on bracket 72. In this way the degree of spark advance or retard under the influence of diaphragm device 22 may be limited.

Inasmuch as the amount of arcuate movement to retard the spark may be diierent than the amount of such movement to open throttle 14, the double spring arrangement 60-'62 whereby distributor controlling rod 58 is connected to diaphragm bracket 42' permits a certain amount of overtravel of the bracket relative to the rod after lever 70 engages one of its stops 76 or 78.

We claim:

l. A charge forming device for an internal combustion engine which includes a distributor for providing timed electrical impulses, said distributor being adjustable to vary the timing of said electrical impulses, an rinduction passage, a throttle valve adjustably mounted in said induction passage for controlling the quantity of air flow through the induction passage, a diaphragm device operatively interconnected with said throttle valve and said distributor, means for rendering said diaphragm device inoperative to affect the operation of said distributor-and said throttle valve under normal engine operating .conditions, conduit means connecting said diaphragm device with a source of engine manifold vacuum, manifold vacuum being of such a value under engine coasting conditions as to actuate said servo device to move .said throttle from a closed to a slightly open position and to actuate said distributor to retard the spark timing.

2.. A charge forming device for an internal combustion engine which includes a distributor for providing timed electrical impulses, said distributor being adjustable t0 vary the timing of said `electrical impulses, an induction passage, a throttle valve adjustably mounted in said induction passage for controlling the quantity of air flow through the induction passage, a diaphragm device, means interconnecting the diaphragm device with said throttle valve and said distributor, lost motion means for rendering said diaphragm device inoperative to affect the operation of said distributor and said throttle Valve under normal engine operating conditions, conduit means connecting said diaphragm device with a source of engine manifold vacuum, manifold vacuum being of such a value under engine coasting conditions as to actuate said servo device to move said throttle from a closed to a slightly open position and to actuate said distributor to retard the spark timing.

3. A charge forming device as set forth in claim l in which the diaphragm device includes lost motion means permitting differential movement between the throttle and the distributor.

4. A charge forming device for an internal combustion engine which includes a distributor for providing timed electrical impulses, said distributor being adjustable to vary the timing of said electrical impulses, an induction passage, a throttle valve adjustably mounted in said induction passage for controlling the quantity of air flow through the induction passage, a diaphragm device, lirst control rod means connecting said device with said throttle valve, second control rod means connecting said device with said distributor, means for rendering said diaphragm device inoperative -to affect the operation of said distributor and said throttle valve under normal engine `operating conditions, conduit means connecting said diaphragm device with a source of engine manifold vacuum, manifold vacuum being of such a value under engine coasting conditions as to actuate said servo device to move said throttle from a closed to a slightly open position and to actuate said distributor to retard the spark timing.

-5. A charge forming device as set forth in claim 4 in which a lost motion mechanism is provided intermediate the diaphragm device and the iirst and second control rod means to permit differential movement between the throttle and the distributor under the influence of said n device.

No references cited. 

